1. Field of the Invention
The present invention relates to radionuclide generators, ion exchange materials for radionuclide generators and methods of making these materials.
2. Description of the Related Art
The use of alpha-emitting radionuclides in the treatment of specific forms of cancers has become increasingly of interest in recent years. Alpha particles are far more effective in the destruction of cancer cells than gamma or beta particles due to their greater linear energy transfer (LET) rates. Bismuth-213 (213Bi) has been identified as an important radioisotope for use in this new field of radiomedicine.
In order for an isotope to be used in medical applications, the isotope should be of high purity to avoid introduction of undesirable radioactive isotopes into the body that would deliver an unnecessary dose to sensitive areas of the body such as the bone marrow. 213Bi is produced as a daughter product in the decay of 229Th, which is itself a daughter product of the decay of 233U. 213Bi has a short half-life of only about 45 minutes, which means that it rapidly decays away once introduced into the body. This also means that the isotope should be supplied in the form of a generator in which a suitable parent isotope is immobilized on an ion exchange material so that the 213Bi can be eluted when required. 225Ac is a parent isotope of choice that can be immobilized and shipped to medical facilities. The 229Th decay series that includes 213Bi is shown in FIG. 1.
Alpha particles are extremely destructive towards conventional organic ion exchange resins, which leads to limited generator life, bleed of undesirable 225Ac into the 213Bi product and the possible release of pyrogens into the aqueous phase during 213Bi elution.
Therefore, there is a need for a radionuclide generator, such as a 213Bi generator, that has improved stability against alpha particles and other forms of ionizing radiation. It would be desirable if the generator provided high separation and high stability in order to yield a solution with substantially no parent isotope and no by products of generator decomposition.